This invention relates to a tray for supporting dental impression material during the making of an impression of a patient""s dentition.
Impressions of patients"" dentitions are produced for a variety of purposes among which are procedures for the manufacture of appliances for bite registrations, crown and bridge constructions, and the like. There generally are five types of impression supporting trays used by a dentist for specific applications. These trays are the posterior, anterior, full arch, quadrant, and sideless posterior. The tray is used simply as a carrier for the impression-forming material and to facilitate the placing and removal of the impression material in and from a patient""s mouth.
In use, the tray is filled with a pliable, uncured putty or silicone impression material and seated in a patient""s mouth until the material sets or cures. Within a few minutes"" time the material will set, but remain pliable and not distort when removed from the patient""s mouth.
When the tray containing the impression material is removed from the patient""s mouth an accurate negative impression of the tooth or teeth requiring the performance of a dental procedure is completed. The negative impression is used to form an accurate duplicate of the patient""s dentition, following which a dental appliance may be produced on a stone model.
Although many different kinds of impression trays are available, not all of them enable good quality dental appliances to be produced. The reasons for this are several, including distortion of the tray due to inadequate rigidity either during the placing of the impression material on the tray or the placing of the tray in the mouth of a patient. Further, other failures of dental appliances are due to the impression material pulling away from the tray borders.
A principal object of the invention is to provide a dental impression tray which overcomes or greatly minimizes the disadvantages referred to above.
A dental impression tray constructed in accordance with one embodiment of the invention has a generally U-shaped frame having two substantially parallel limbs joined at corresponding ends by a connector. Each limb has a buccal or outer edge and a lingual or inner edge. Adjacent the outer edge of each limb is an upstanding wall. Adjacent the inner edge of each limb is a plurality of upstanding projections spaced from one another and also spaced from the adjacent outer wall. The space between the outer wall and the projections of each limb forms a web. Each web is pierced by a plurality of longitudinally spaced apertures or openings.
In one embodiment the outer wall of each limb extends uniformly in opposite directions from the level of the associated web. The projections associated with each limb also extend in two opposite directions from the level of the web. The height of the projections from the level of the associated web preferably is less than the height of the outer wall.
The connector which joins the corresponding ends of the limbs preferably is thinner than the limbs themselves, thereby facilitating the ability of the dental technician to place a tray in an appropriate position in a patient""s mouth.
Spanning the limbs and preferably integrally molded with the latter is a support for dental impression material. The support preferably is of mesh construction having openings therein through which the dental impression material may pass from one side of the support to the other.
In those instances in which the dental practioner wishes to make an impression of both the upper and lower teeth of a patient, the uncured dental impression material may be placed on both sides of the support prior to placing the tray in a patient""s mouth. When the tray is placed in the patient""s mouth and the patient clinches his jaw to form an impression in the impression material of both the upper and lower teeth, the outer walls will restrict outward movement of the impression material, the projections will restrict inward and longitudinal movements of the impression material, and the openings formed in the web and in the support mesh will provide an interlock between those portions of the impression material on opposite sides of the webs and the support.
In another embodiment of the invention the tray has the limbs, projections, apertures, and impression material support as described above. However, the outer walls and the inner projections extend upwardly from one side only of the limbs.